Juvenile Idiopathic Arthritis Causes

The cause of juvenile idiopathic arthritis is unknown. Like adult-type RA and many other related diseases, JIA is an autoimmune disease. This means that the body's immune system mistakenly attacks the tissues it is supposed to protect.

The chronic inflammation of the synovium (the fluid-producing tissue that surrounds the joints) is linked to greater-than-normal activity of the immune system.

Normally, the immune system fights "assaults" by "invaders" such as infections or blood or tissue from another person.

The immune system produces specialized cells and proteins, which are released into the bloodstream to fight off the "invaders." One important type of immune protein is called an antibody.

In autoimmune diseases, the cells and antibodies of the immune system attack the body's own tissues. In the case of arthritis, the attack is directed against the synovium, which becomes inflamed.

The inflammation causes the synovium to thicken and grow abnormally. As the synovium expands outside of the joint, it presses on and eventually damages the bone and cartilage of the joint and the surrounding tissues such as ligaments and tendons.

We do not know what causes the inappropriate autoimmune response. Because the cause has not yet been discovered, we use the term "idiopathic" which means "of unknown cause."

Emotional factors and diet do not appear to be risk factors for JIA.

According to statistics from the Arthritis Foundation, there are at least 300,000 children in the U.S. with JIA.